Condensed Schedule of Investments (Parenthetical) - U.S. Government Securities [Member] - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
U.S. Treasury bills, 0.205% [Member]
Schedule of Investments [Line Items]
Investment in U.S. Treasury bills, Amortized cost	$ 3,998,838
Investment, interest rate	0.205%
Face amount	$ 4,000,000
Maturity date	Jul. 07, 2016
U.S. Treasury bills, 0.265% [Member]
Schedule of Investments [Line Items]
Investment in U.S. Treasury bills, Amortized cost	$ 11,993,728
Investment, interest rate	0.265%
Face amount	$ 12,000,000
Maturity date	Aug. 11, 2016
U.S. Treasury bills, 0.015% [Member]
Schedule of Investments [Line Items]
Investment in U.S. Treasury bills, Amortized cost		$ 32,748,076
Investment, interest rate		0.015%
Face amount		$ 32,750,000
Maturity date		Mar. 03, 2016
U.S. Treasury bills, 0.0125% [Member]
Schedule of Investments [Line Items]
Investment in U.S. Treasury bills, Amortized cost		$ 22,749,281
Investment, interest rate		0.0125%
Face amount		$ 22,750,000
Maturity date		Jan. 21, 2016